In order to improve fuel efficiency or reduce exhaust emission, some cars having an internal combustion engine such as an engine include what is called an idling-stop (or economy-running) function, in which an engine is automatically stopped while a vehicle stops and a driver operates a brake pedal, and the vehicle is automatically re-started, for example, by a driver's operation for re-start such as decrease in an amount of operation of a brake pedal to zero.
In this idling-stop, the engine may be re-started while an engine rotation speed is relatively high. In such a case, with a conventional starter in which pushing-out of a pinion gear for rotating the engine and rotation of the pinion gear are caused by one drive command, the starter is driven after waiting until the engine rotation speed sufficiently lowers, in order to facilitate engagement between the pinion gear and a ring gear of the engine. Then, a time lag is caused between issuance of a request to re-start an engine and actual engine cranking, and the driver may feel uncomfortable.
In order to solve such a problem, European Patent Publication No. 2159410 (PTL 1) discloses a technique, with the use of a starter configured such that a pinion gear engagement operation and a pinion gear rotational operation can individually be performed, for causing a pinion gear to perform a rotational operation prior to the pinion gear engagement operation when a re-start request is issued while a rotation speed of an engine is being lowered.